Non-malignant asbestos-related diseases in Brazilian asbestos-cement workers

Production of asbestos-cement products in Brazil started in the 1940s, peaked in the 60-70s and is still an active industry. This study was designed to assess the non-malignant effects of asbestos exposure in the asbestos-cement industry in Brazil.

A group of 828 former asbestos-cement workers enrolled in a cross-sectional and cohort study of respiratory morbidity, submitted to a detailed occupational history, respiratory symptoms questionnaire, spirometry, PA chest x-ray, and high resolution computed chest tomography (HRCT). Asbestos exposure was assessed by years of exposure, cumulative exposure (a semi-quantitative method), and latency time from first exposure. Asbestosis and pleural thickening were assessed according to HRCT criteria.

Asbestosis was present in 74 (8.9%) and pleural thickening in 246 (29.7%). Using the HRCT as the "best available evidence", it was shown that were more false negatives than false positives in the x-ray readings for parenchymal (21.6% false negatives, 4.2% false positives) and pleural (26.0% false negatives, 14.4% false positives) diseases due to asbestos. Latency time from first exposure was the best predictor for both asbestosis and pleural thickening. Subjects in the higher exposure groups presented lower levels of lung function. Obstructive defects were significantly related to smoking, shortness of breath, body mass index, and age, whereas restrictive defects were related to asbestosis, shortness of breath, and latency time. Chronic bronchitis increased with latency time in the three smoking groups and was significantly related to pleural thickening (OR 1.56 (1.00-2.42)). Shortness of breath was significantly associated with body mass index and pleural thickening (OR 1.30 (1.24-2.09)).

Pleural thickening and asbestosis showed a significant association with latency time and exposure. FVC and FEV(1) decreased across increasing profusion with an added effect of pleural thickening. There was a significant and independent effect of exposure on lower levels of FVC and FEV(1). Obstructive defects were mainly related to smoking and restriction to asbestosis. Dust exposure and smoking were synergistic in increasing chronic bronchitis and shortness of breath report. Shortness of breath report was also related to pleural thickening and higher body mass index.